Effect of drying on biofilter performance:: Modeling and experimental approach

The moisture content of biofilter media is a key parameter for its adequate performance. Control of moisture requires a better understanding of the drying of the support due to changes in inlet air temperature and relative humidity and from metabolic heat production by pollutant oxidation. A dynamic one-dimensional model was developed to describe drying and its effect on biofilter performance. Mass and energy balances were established on an elementary representative volume. The biological reaction term incorporated temperature, water content, and pollutant concentration effects. The model describes the variations in pollutant concentration, air relative humidity, temperature, and water content of the media. It predicts (1) water evaporation from the packing material as a consequence of metabolic heat generation and variations of the relative humidity of the inlet air stream, and (2) the resulting decrease in biofilter performance. The model was validated with biofiltration experiments treating gaseous toluene using peat as support. Various ranges of inlet air relative humidity, temperature, air velocity, and inlet pollutant concentration were assayed.